If you want to plant edibles, you might try:
lettuce (warm season variety: prizeleaf, kweik)
chinese cabbage (if you can keep it watered)
reg'lar cabbage (if you cover it with floating row cover or recycled
gauzy curtains to keep the bugs off)
carrots/beets/turnips

All these should have time to mature yet this season. If you want to
plant non-edible (ie, green manure) try: legume (white clover, alfalfa)
non-legume fast: buckwheat, ANNUAL ryegrass slow: winter oats